Google's executive chairman Eric Schmidt kicked off the annual D: All Things Digital conference with a bang on Tuesday night in a wide-reaching interview on the current state of the technology industry, his new role at Google, what he really thinks about privacy, and his opinions about Google's main rivals.

The most interesting part of the conversation was when Schmidt talked about his "gang of four." He said Google, Apple, Amazon, and Facebook have built platforms that are driving today's consumer revolution in technology.

"We've never had four companies growing at the scale those are, in aggregate," Schmidt said.

In the past, it has typically been one company and one big platform at the center of the technology world, Schmidt said, and he pointed to IBM and Microsoft as the leaders of previous eras.

However, he doesn't see Microsoft as one of the main players anymore. He suggested that there's a big drop-off after today's big four and it was debatable who the fifth and sixth big platform companies were. But, he mentioned PayPal and Twitter as his picks.

Schmidt did throw Microsoft a bone. He said the company still has a lot of enterprise business locked up and is doing well with Windows Server. Clearly, Schmidt lumps Microsoft in with Oracle, SAP, and others as enterprise platforms that are separate from the consumer powerhouses he sees as today's tech leaders. In fact, went a step further, suggesting that enterprise and traditional IT platforms are under attack.

"What you are seeing is the death of IT as we know it... With this new technology you don't need as much of it." Schmidt said. He sees complex enterprise systems being replaced by cloud services.

When I posted that quote on Twitter Tuesday night during Schmidt's interview, @jordanmdtx replied, "'Death' would be better described as 'transformation.'" I think Jordan is exactly right about that, but there's likely to be continued upheaval in IT during the transformation.

The other interesting thing Schmidt said was that he doesn't see all four of his big four continuing to dominate. He said, "It's unlikely one of the four will acquire another because of antitrust issues. More likely is one begins to miss the mark."

My ZDNet colleague Larry Dignan thinks Google is most likely to stumble. I think it's Facebook. Facebook has the worst platform of the four. It's the most difficult to use. It's already blown its shot at gaining users' trust. And, it's likely to come under pressure from new competitors over the next year. Plus, there's a natural cyclical phenomenon to social networks. I wouldn't be surprised to see a lot of the crowd move to something else within 24-36 months.

For more on the Schmidt interview, here is a nine-minute clip that highlights Schmidt's remarks at D9: